Telescopic slides for file drawers and the like are often desirable for use in cabinets and other rack mounted applications. Such slides permit easy access to the interior of the drawer. The slides maintain the drawer in a horizontal position regardless of how far the drawer is withdrawn from the cabinet. A typical telescopic drawer slide has two or three slide members, often slidably secured to each other by sets of ball bearings riding in raceways formed on the slide members.
Three element telescopic slides normally include an outer slide member, an intermediate slide member, and an inner slide member. The outer slide member is connected to the cabinet or enclosure. The slide member affixed to the drawer is the inner slide member. The intermediate slide member is slidably connected to both the outer and inner slide members. In such a configuration, when the drawer is in a fully-open position the slide members will be positioned such that the intermediate slide member is extended relative to the outer slide member and the inner slide member is extended relative to the intermediate slide member.
In certain applications, it is desirable for a drawer to be able to be opened from both the front and the rear of a cabinet or rack. Such a drawer may be called a two-way drawer, the two-way drawer allowing access to the contents of the drawer from the front and rear end of the cabinet. The slide for such a drawer may be called a two-way slide. It is desirable in a two-way drawer to avoid having the intermediate slide member, which is connected neither to the drawer nor to the cabinet, from protruding from either end of the cabinet when the drawer is in a closed position. If the intermediate member does protrude from the cabinet and the drawer is in a closed position, users of the cabinet, or other people, may injure themselves by bumping against the protruding intermediate slide member. Equipment may also be damaged by bumping against a protruding intermediate slide member. The intermediate slide member may also be damaged in such a situation.
Furthermore, a typical drawer is supported by two slide assemblies, one at each side. It is desirable that the slide members of both slide assemblies extend in the same order. This is so because for a given total extension of the slide assembly the vertical deflection under a given load may be dependent on the specific relative extensions of the inner and intermediate slide members. If the two slide assemblies have not extended in the same order the drawer will have a tendency to tilt toward the weaker side.
A two-way slide assembly is disclosed in German Pat. DE 3930713 A1. An embodiment of such a two-way slide assembly is shown in FIGS. 1-4. This two-way slide has an inner slide member 11, an outer slide member 13 of substantially the same dimensions as the inner slide member 11, and an intermediate slide member 15 that fits within and between the inner slide member 11 and the outer slide member 13. All of the slide members 11, 13, and 15 are of substantially the same length. This two-way slide prevents the protrusion of the intermediate slide member 15 in the closed or retracted position through the use of end stops 17, 19, mounted on arms 21 near each end of the intermediate slide member 15.
The end stops 17, 19 are small wheels which run along raceways 23 and 25 of the inner slide member 11 and the outer slide member 13. The distance between the end stops 17, 19 mounted on the arm 21 is greater than the distance between raceways 23 and 25. At each end of the intermediate slide member one end stop 17 runs in a raceway 23 of the inner slide member 11 and the other end stop 19 runs in a raceway 25 of the outer slide member 13. Referring now to FIG. 4, the intermediate slide member 15 is prevented from traveling in one direction with respect to the inner slide member 11 due to the end stop 19 contacting the inner slide member 11.
When the slide is in the fully closed position, however, the end stops 17, 19 protrude from the ends of the slide. Additionally, the inner slide member 11, and outer slide member 13 are the same dimensions, thus preventing true telescopic action.
Mounting two slide members, namely the inner slide member 11 and the outer slide member 13, of substantially the same dimensions, with the intermediate slide member 15 mounted within them, necessarily increases the overall width of the slide assembly. The extra width is undesirable because it increases the necessary clearance between the drawer and the cabinet. Protruding end stops are also undesirable. Protruding end stops limit the possible extension of the drawer by requiring space in a closed drawer that would otherwise be available for the slide members. Protruding end stops also subjects the end stops to possible damage. Furthermore, the use of end stops does not provide for a method to sequence the extension of the slide members.
A telescopic drawer slide with a mechanical sequencing latch is shown in U.S. Pat. No. 5,551,775 by Jackie D. Parvin, the disclosure of which is incorporated by reference herein. This slide, however, does not provide for the possibility of two-way travel.